Consider an example in which we measure the percent body fat, height (in inches), and waist size (in inches) of a group of people. What might you expect the simple regression relating percent body fat to height would look like? An example for one sample might be:
Body Fat % = 13.012 − 0.031 × Height
In this example, there is almost no discernible relationship between height and percent body fat. This information could be useful, but suppose we still want to come up with a good model for predicting body fat.